This project includes a study of changes in prostaglandin synthesis in rheumatoid synovial cells in tissue culture through alterations in the fatty acid composition of cell lipids. Eiocosapentaenoic acid treated cells produce small quantities of PGE3 and reduced quantities of PGE2, compared to arachidonic acid-treated cells. Other studies will investigate the effects of alterations in the fatty acid composition of diets on model inflammatory reactions in experimental animals. Stimulation of PG synthesis by an 18,000 molecular weight factor isolated from rheumatoid synovial explant cultures and the mechanism of PG synthesis by this factor is under study. Finally, a method for the analysis of synovial PGs in pathologic human synovial fluids by a combination of high performance liquid chromatography and radioimmunoassay is being developed.